# Oldest Reference to Astronomical Seeing

I'm writing a paper on astronomical seeing. Sir Isaac Newton identified both the phenomenon and origin of astronomical seeing in his Opticks. He writes:

If the Theory of making Telescopes could at
length be fully brought into Practice, yet there would
be certain Bounds beyond which Telescopes could
not perform. For the Air through which we look
upon the Stars, is in a perpetual Tremor; as may be
seen by the tremulous Motion of Shadows cast from
high Towers, and by the twinkling of the fix'd Stars.


is anyone aware of any older reference from Gilbert, Galileo, Harvey, Ptolemy, Copernicus or Kepler?

• You may also want to try asking this question in the astronomer's Facebook group. – pela Jan 26 '16 at 10:46
• As you probably already knew, Ptolemy's "Optics" computes refraction angles, but treats these as constant. – user21 Jan 26 '16 at 14:04